General Physics

The Exploratorium - http://www.exploratorium.edu/snacks/index.html
Physics 4 Kids - http://www.physics4kids.com/

Forces

Force and Motion from the Full Option Science System - http://www.fossweb.com/modulesMS/ForceandMotion/index.html
Engineering Interact Animation that shows gravity, friction, compression, stretching and magnetic forces in a fun way, at 'Parkworld', an amusement park.

Simple machines

Take digital photos (or find CC images on the web) of the following six simple machines:

1. inclined plane
2. wedge
3. lever
4. screw
5. pulley
6. wheel-and-axle

Upload your photos onto Voicethread and describe how each of them works to make a job easier.
Inventors Toolbox - The elements of machines (phots and descriptions) - http://www.mos.org/sln/Leonardo/InventorsToolbox.html
Gadget Anatomy - a short quiz about the simple machines that make up more complex machines - http://www.mos.org/sln/Leonardo/GadgetAnatomy.html
A worksheet - "If Simple machines were not around...?" http://www.teach-nology.com/worksheets/science/simpmach/if/
Simple machines game from the Museum of Science and Industry - http://www.msichicago.org/fileadmin/Activities/Games/simple_machines/

Energy

Energy Quest - Science projects about energy - http://www.energyquest.ca.gov/projects/index.html

Electrical Circuits

Flash animation to create circuits - http://www.engineeringinteract.org/resources/siliconspies/flash/concepts/buildingcircuits.htm

Light

Optical Illusions - http://www.michaelbach.de/ot/

Sound

This video shows students from Mrs Laguna's crushing cans without any force on their part - what causes the cans to collapse?